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/* drivers/misc/lowmemorykiller.c
*
* Copyright (C) 2007-2008 Google, Inc.
*
* This software is licensed under the terms of the GNU General Public
* License version 2, as published by the Free Software Foundation, and
* may be copied, distributed, and modified under those terms.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
*/
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/oom.h>
#include <linux/sched.h>
#include <linux/nodemask.h>
#include <linux/vmstat.h>
#include <linux/notifier.h>
static int lowmem_shrink(int nr_to_scan, gfp_t gfp_mask);
static struct shrinker lowmem_shrinker = {
.shrink = lowmem_shrink,
.seeks = DEFAULT_SEEKS * 16
};
static uint32_t lowmem_debug_level = 2;
static int lowmem_adj[6] = {
0,
1,
6,
12,
};
static int lowmem_adj_size = 4;
static size_t lowmem_minfree[6] = {
3 * 512, /* 6MB */
2 * 1024, /* 8MB */
4 * 1024, /* 16MB */
16 * 1024, /* 64MB */
};
static int lowmem_minfree_size = 4;
static struct task_struct *lowmem_deathpending;
#define lowmem_print(level, x...) \
do { \
if (lowmem_debug_level >= (level)) \
printk(x); \
} while (0)
module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);
module_param_array_named(adj, lowmem_adj, int, &lowmem_adj_size,
S_IRUGO | S_IWUSR);
module_param_array_named(minfree, lowmem_minfree, uint, &lowmem_minfree_size,
S_IRUGO | S_IWUSR);
module_param_named(debug_level, lowmem_debug_level, uint, S_IRUGO | S_IWUSR);
static int
task_notify_func(struct notifier_block *self, unsigned long val, void *data);
static struct notifier_block task_nb = {
.notifier_call = task_notify_func,
};
static int
task_notify_func(struct notifier_block *self, unsigned long val, void *data)
{
struct task_struct *task = data;
if (task == lowmem_deathpending) {
lowmem_deathpending = NULL;
task_free_unregister(&task_nb);
}
return NOTIFY_OK;
}
static int lowmem_shrink(int nr_to_scan, gfp_t gfp_mask)
{
struct task_struct *p;
struct task_struct *selected = NULL;
int rem = 0;
int tasksize;
int i;
int min_adj = OOM_ADJUST_MAX + 1;
int selected_tasksize = 0;
int selected_oom_adj;
int array_size = ARRAY_SIZE(lowmem_adj);
int other_free = global_page_state(NR_FREE_PAGES);
int other_file = global_page_state(NR_FILE_PAGES);
int node;
/*
* If we already have a death outstanding, then
* bail out right away; indicating to vmscan
* that we have nothing further to offer on
* this pass.
*/
if (lowmem_deathpending)
return 0;
for_each_node_state(node, N_HIGH_MEMORY) {
struct zone *z =
&NODE_DATA(node)->node_zones[ZONE_DMA];
other_free -= zone_page_state(z, NR_FREE_PAGES);
other_file -= zone_page_state(z, NR_FILE_PAGES);
}
if (lowmem_adj_size < array_size)
array_size = lowmem_adj_size;
if (lowmem_minfree_size < array_size)
array_size = lowmem_minfree_size;
for (i = 0; i < array_size; i++) {
if (other_free < lowmem_minfree[i] &&
other_file < lowmem_minfree[i]) {
min_adj = lowmem_adj[i];
break;
}
}
if (nr_to_scan > 0)
lowmem_print(3, "lowmem_shrink %d, %x, ofree %d %d, ma %d\n",
nr_to_scan, gfp_mask, other_free, other_file,
min_adj);
rem = global_page_state(NR_ACTIVE_ANON) +
global_page_state(NR_ACTIVE_FILE) +
global_page_state(NR_INACTIVE_ANON) +
global_page_state(NR_INACTIVE_FILE);
if (nr_to_scan <= 0 || min_adj == OOM_ADJUST_MAX + 1) {
lowmem_print(5, "lowmem_shrink %d, %x, return %d\n",
nr_to_scan, gfp_mask, rem);
return rem;
}
selected_oom_adj = min_adj;
read_lock(&tasklist_lock);
for_each_process(p) {
struct mm_struct *mm;
int oom_adj;
task_lock(p);
mm = p->mm;
if (!mm) {
task_unlock(p);
continue;
}
oom_adj = p->oomkilladj;
if (oom_adj < min_adj) {
task_unlock(p);
continue;
}
tasksize = get_mm_rss(mm);
task_unlock(p);
if (tasksize <= 0)
continue;
if (selected) {
if (oom_adj < selected_oom_adj)
continue;
if (oom_adj == selected_oom_adj &&
tasksize <= selected_tasksize)
continue;
}
selected = p;
selected_tasksize = tasksize;
selected_oom_adj = oom_adj;
lowmem_print(2, "select %d (%s), adj %d, size %d, to kill\n",
p->pid, p->comm, oom_adj, tasksize);
}
if (selected) {
if (fatal_signal_pending(selected)) {
pr_warning("process %d is suffering a slow death\n",
selected->pid);
read_unlock(&tasklist_lock);
return rem;
}
lowmem_print(1, "send sigkill to %d (%s), adj %d, size %d\n",
selected->pid, selected->comm,
selected_oom_adj, selected_tasksize);
lowmem_deathpending = selected;
task_free_register(&task_nb);
force_sig(SIGKILL, selected);
rem -= selected_tasksize;
}
lowmem_print(4, "lowmem_shrink %d, %x, return %d\n",
nr_to_scan, gfp_mask, rem);
read_unlock(&tasklist_lock);
return rem;
}
static int __init lowmem_init(void)
{
register_shrinker(&lowmem_shrinker);
return 0;
}
static void __exit lowmem_exit(void)
{
unregister_shrinker(&lowmem_shrinker);
}
module_init(lowmem_init);
module_exit(lowmem_exit);
MODULE_LICENSE("GPL");
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